1. Field of Invention
The invention relates to a piezoelectric ink-jet printhead that has a cavity unit including a plate with a damper wall.
2. Description of Related Art
As disclosed in U.S. Pat. No. 5,943,079, which is incorporated herein by reference, a prior art on-demand type ink-jet printhead includes a cavity plate, a piezoelectric plate, and a vibration plate (flexible film) placed as a diaphragm between the cavity plate and the piezoelectric plate. The cavity plate is formed with nozzles, pressure chambers communicating with the respective nozzles, and an ink manifold that communicates with the pressure chambers to supply ink thereto. The piezoelectric plate is provided with energy generating portions, such as piezoelectric elements, that are selectively driven to pressurize the ink in the pressure chambers for ejection though the nozzles.
When any energy generating portion is driven, the corresponding pressure chamber is pressed and the pressure is transmitted to the corresponding nozzle, and an ink droplet is ejected from the nozzle to perform printing. When the pressure chamber is pressed, the pressure wave acting on the pressure chamber contains not only forward components directed toward the nozzle but also backward components simultaneously directed toward the ink manifold. As a result, so-called crosstalk between the forward and backward components may occur. To absorb and lessen the backward components, a damper is provided for the ink-jet printhead. A damper chamber is formed as a recess in the piezoelectric plate to face the ink manifold. The vibration plate (flexible film) extends to separate the damper chamber from the vibration plate (flexible film). A hole (air vent) is formed at a side of the piezoelectric plate (flexible film) at half the plate thickness such that the damper chamber communicates with the atmosphere.
However, the vibration plate (flexible film), which extends to separate the damper chamber from the ink manifold, can be used for only the structure where the pressure chamber and the ink manifold are arranged in the same plane of the cavity plate. In that structure, the energy generating portion and the damper chamber are also arranged in the same plane of the piezoelectric plate, and thus the width of the printhead in a direction perpendicular to the nozzle array becomes large. In addition, three-dimensional machining of the pressure chamber, ink manifold, and nozzles in the same cavity plate is difficult and requires many processes.
Another ink-jet printhead is disclosed in FIG. 4 of U.S. Patent Application Publication No. 2001/0020968, which is incorporated herein by reference in its entirety. A cavity unit of the ink-jet printhead is formed by laminating a plurality of plates, that is, a base plate formed with pressure chambers, a manifold plate formed with an ink manifold, a spacer plate interposed between the base plate and the manifold plate, and a nozzle plate formed with nozzles. In that structure, the width of the printhead in a direction perpendicular to the nozzle array can be reduced, and the pressure chambers, ink manifold, and nozzles can be machined easily in the respective plates. However, this structure does not allow a damper chamber to be formed to face the ink manifold in the manifold plate. If the manifold plate is made partially thin so as to be vibrated by a pressure wave, the rigidity of the printhead is partially reduced, and the ink ejection characteristics may vary among the nozzles.